KIEV, Ukraine – Ukraine's acting president has called for the formation of a national guard and for the mobilization of reserves and volunteers into the country's armed forces in order to counter Russian military aggression.

Oleksandr Turchynov on Tuesday asked the national parliament to approve a decision to turn the country's Interior Ministry troops into a National Guard whose aim "is to defend the country and citizens against any criminals, against external and internal aggression."

Turchynov said that the mobilization will cover those who have previously served in the army as well as volunteers.

Russian forces have strengthened their control over Ukraine's Crimea region in the run-up to a contentious referendum set for Sunday on whether to split off and become part of Russia.